<!DOCTYPE html>
<html lang="zh">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>透明度</title>
  <style>
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }

    body {
      background-image: url(../../素材/images/dog1.webp);
    }

    .box {
      position: absolute;
      left: 50%;
      top: 50%;
      margin-left: -275px;
      margin-top: -134px;

      width: 551px;
      height: 268px;
      background-image: url(../../素材/images/BG01.png);

      /* 透明度 */
      opacity: 0.5;
    }
  </style>
</head>

<body>
  <div class="box"></div>
</body>

</html>